Identify this component?

[Essi]

Hey!

Does anyone recognice this part?

It`s marked with C306 (ST- Sign) FRO169.

It looks like a transistor or diode in SOT-229 package.

Thanks!

Frank

[Peter BENSCH]

Welcome @Essi, to the community!

It is a device in the package type ISOTOP. Could you please check the long sides, i.e. on your photo the left and right sides, whether anything can be read there?

Additionally, it would be helpful to know where the device was used and, if possible, also its immediate circuit neighbours.

Regards
/Peter

[Essi]

Hello Peter!

Thanks for your answer.

This component is part of a welding machine.

It is surrounded by MOSFETs ( like APT5010JLL ). After rectification,
these normally generate a square wave voltage.

The component has no other markings on its faces...

I think they are dual diodes. I determined this by measuring with a
voltmeter.

Regards,

Frank

[Peter BENSCH]

Well, even with a MOSFET, e.g. the STE36N50DK, which was discontinued a long time ago, or IGBTs and TRIACs diode paths are measurable. If the device is not completely destroyed, MOSFETs still have the always-present parasitic diode path between drain and source; devices such as the STE35N50DK mentioned also have an additional freewheeling diode.

I agree with you, though: if MOSFETs are already arranged around there, it is probably a dual diode, with the diode paths either between 1-2 and 3-4, or between 1-3 and 4-2, respectively (order A-K each on your image).

Regards
/Peter

[drakeshawn]

It is probably an STMicroelectronics high-power transistor (not a diode), but the exact model needs the circuit context or picture to be sure.

[Essi]

Hello Shawn!

Unfortunately, I don´t have a circuit diagram.

The manufacturer of the welding machine ( Fronius, Austria ) doesn´t
release any technical documentation.

I belive it is a double diode. Terminals 1 - 3 and 2 - 4 are connected
in parallel on the PCB.

Terminals 1 - 3 go to the positive terminal of a capacitor.


Regards, Frank

[Peter BENSCH]

Ah, that explains the marking FRO169. Documentation for such customer-specific devices, which is always subject to an NDA, is held exclusively by that customer - in this case, Fronius. If you do not receive any documents or guidance from Fronius, unfortunately no one else can help you.

But at least you have already figured out the pinout; together with the maximum D-S voltage and the MOSFET’s maximum current, you can already draw conclusions.

Good luck!

Regar
/Peter